OPINION:
With Government economic aspirations for aquaculture ballooning to cosmic heights, and Northland Regional Council's proposals to create an aquaculture industry in Northland worth $300 million by 2030 largely through expansion of finfish farming, there is a desperate need to understand the ecological and environmental implications of such a move to balance the unrealistic economic arguments in favour of a huge expansion in aquaculture.

Despite glowing reports from vested interests on the economic benefits of finfish farming, there is little appreciation of what this farming may harm in terms of the environmental qualities of local waters and seabed, the impacts on public amenity values, and the long term impacts on natural fish stocks. There is little understanding, and no analysis, of the economic impacts of further damaging our already dented ''100% clean green New Zealand'' image promoted by Tourism NZ in 1999. We are rapidly falling away from the high standing we had internationally in this regard 13 years ago (dropped from #1 to #14!).

It is very likely that any economic advantage coming from future aquaculture, will be balanced by a similar or greater economic loss brought about by international realization that our clean green image is a myth. In the meantime we will have damaged our environment to such a point that, even if we get our act together in terms of environmentally damaging developments, we will not be able to turn back the clock to where we were in 1999. We will have fallen into the same hole that the rest of the world dug for itself some years ago. Protecting our environment and international reputation is vital to our future economic wellbeing. Aquaculture is just one aspect of this much bigger problem, but is what I concentrate on here.

Here I list some of the more obvious real or potential problems associated with sea-cage finfish farming. I will concentrate on environmental, biological and ecological matters, leaving those equally serious planning, social, tourism and amenity aspects to experts in those fields. Finally I will comment on what criteria I would consider to provide an acceptable model for marine finfish farming.

Philosophy of farming versus wild fish managementAccording to international reports, the world's major wild fish stocks have been reduced to around 10% of their pre-fished biomass. Such massive reduction in wild stocks has serious and widespread environmental impacts, but is also one of the major economic drivers behind the apparent viability of finfish aquaculture as an alternative. Finfish farming is not about feeding the world. It is about a few people making lots of money by producing high-quality products for the top-end of the market, but unfortunately it seems to be at the expense of other people and the environment.

There is an increasing realisation that rather than trying to achieve the maximum possible sustainable yield from a fishery by fishing it down to around 20% of pre-fished biomass with its attendant impacts on the environment, we should be leaving more fish in the sea, thus promoting a healthier ocean environment with greater benefits to more people and the natural functioning ecology. MPI Fisheries is on a path to moving snapper stocks up from the current target of 23% of pre-fished biomass, to 40% of pre-fished biomass! This is a major and very welcome change in philosophy which should be encouraged. Doing the same thing for most other commercial species, particularly crayfish in a Northland context, would see major improvement in the ecology of our presently degraded shallow reefs.

I am left with the thought that a more conservative and realistic approach to wild fish management would have far greater long term economic and environmental values than pursuing sea-cage finfish farming for the short-term economic gain of a few people at the expense of many and of the environment.

Feeding the fish farmsThe vast majority of finfish farms are fed on fish caught in the wild. The conversion efficiency is generally pretty poor. My understanding is that for every one kilogramme of consumable product from a finfish farm, between 5 and 8 kilogrammes of wild-caught fish is required. So far from taking pressure off fish in the wild, finfish aquaculture dramatically increases the impact of fishing on wild stocks, and there will be a demand for large quantities of ''trash'' fish of virtually any species to provide fish meal and other products to keep the finfish farms operating. The potential impacts on the marine ecology are huge.

There are some moves to use trash protein from other fishing activities (fish frames etc.) and agricultural waste (chicken, meat industry etc.) but the projected finfish farming scale will soon outstrip the supply of such alternatives. There is also limited capacity to use vegetable protein products in fish food.

One of the worst examples of inappropriate feed stocks for finfish farming is the situation in West Africa, where industrial-scale trawling for anything catchable is used to make fish-meal to feed penned stocks of endangered Atlantic bluefin tuna held in Mediterranean ''tuna ranches'', ultimately destined for the insatiable elite Japanese market. Meanwhile the people of West Africa are starving because their fish stocks have been taken.

Seabed impacts and water qualityA proportion of the food offered to fish in sea-cages is not eaten and falls through the cage floor on to the seabed. Here, along with large quantities of fish faeces, it overwhelms any natural scavengers that may attempt to consume it, and basically rots on the seabed, using up oxygen and causing anoxic dead zones. Not only does this have serious impacts on benthic ecology, but in some circumstances can lead to production of toxic algal blooms. These can kill the fish in the pens, or force the evacuation of the area and towing the cages to a safer place, such as has happened in a Stewart Island salmon farm. In the quiet inlet of Whangaroa Harbour where I understand the current proposal for a fish farm is based, such a problem is very likely to happen.

Downstream drift of fish faeces and uneaten food also impacts on local water quality. Large-scale finfish farming can produce faecal matter in quantities equal to that from human populations in small towns.

Such problems can be minimized by placing finfish farms in areas of strong currents or on open coasts where coastal currents and wave action maintain a high degree of flushing. These locations also often cause conflict with other users.

Diseases, antibiotics and other medicationsFinfish farming inevitably is done at high stocking rates, where large numbers of fish are confined to a small area. This drastically increases the risk of disease and cross-infection within the caged stock. In some cases contaminated feed can introduce diseases to an otherwise healthy fish farm stock.

Fish farmers sometimes use antibiotics, or other medications, in the feed to treat or to attempt to prevent diseases in the fish stock. These medications get into the local waters where they may cause unwanted problems to wild fish.

Gene pool of farmed fishSnapper, kingfish and hapuku ''fingerlings'' are supplied to sea-cage finfish farms from a hatchery which specialises in production of young fish up to a size where they can be placed in the cages. Currently the main, and possibly only, facility producing the fish is the NIWA hatchery at Ruakaka. A small breeding stock of each species is held there, which produces all the hundreds of thousands of fingerlings required for future fish farms.

When I visited the facility around four years ago, the breeding stock for each species consisted of around 30 fish, selected from the wild from a range of locations. Ultimately the genetic basis for the stock for all the fish farms supplied from this facility is extremely small compared to that of a wild-produced stock where many thousands of fish would have contributed to the resulting gene pool.

Fish produced in the hatchery are looked after extremely well and many individuals survive early life in the hatchery. A very large proportion of those fish if raised in the wild, however, would never have made it to fingerling size, and would have been stripped from the population by natural selection. We all know the term ''survival of the fittest'', which largely refers to genetic fitness as well as physical fitness. The artificial breeding process has established in the hatchery-raised stock many ''genetic weaklings'' which would not have survived in the wild.

I believe there are potential long-term implications for both wild and farmed fish stocks of the small gene pool held in the farmed stocks. There is an unnatural genetic bottle-neck created by fish farming in this way. Farmed fish are thus ''genetically weaker'' than wild stocks of fish, and will be less capable genetically of coping with future environmental variations which are likely to increase under climate change scenarios.

Impacts of escapes and releasesDespite all efforts to contain fish in sea-cages, accidental escapes always happen. There have also been deliberate large-scale releases of kingfish and snapper from the Ruakaka facility, with fish released in Kawau Bay and off Whangarei several years ago when a proposed sea-cage farm was refused consent near Bream Head. Hundreds of thousands of juvenile fish raised and intended for that farm were released with suitable fanfare as a re-stocking enhancement measure for the wild population. In fact it will have ''polluted'' the wild population with inferior stock from an unnaturally small gene pool, pampered and raised artificially to produce a high proportion of genetic weaklings most of which would never have survived to that size in the wild.

As discussed earlier, diseases frequently occur in finfish sea-cages because of high stocking rates and fish being confined in close quarters. When escapes or releases occur, these diseased fish then mingle with wild fish where diseases can spread. Imported feed components can bring hitherto unknown fish diseases into the country.

Biosecurity risksApart from the potential disease risks from imported feed components mentioned above, there are other biosecurity risks associated with most marine aquaculture ventures. One of these relates to movement of used equipment, stock, and associated vessels between aquaculture areas locally, regionally and nationally.

There is a high risk of spreading unwanted invasive organisms from one farm to another on contaminated equipment or vessels, and in some cases attached to actual farm stock being moved to another location. I believe that the spread of the invasive seaweed Undaria from the Cook Strait area to the Firth of Thames was probably facilitated by moving used and contaminated mussel farming equipment during establishment of the Wilson's Bay farms. Contaminated lines of seed stock from Kennedy Bay carried Undaria to mussel farms in Port Fitzroy on Great Barrier Island.

Recreational and commercial boats further spread the pest earlier to Auckland Harbour and Tauranga. I would not be surprised if Undaria has been transported to the mussel farm off Houhora, though I don't think anyone has bothered to look despite my repeated requests.

There are several species of marine invaders of concern in the Auckland and Northland areas, many of which are often first seen on artificial structures. The proliferation of finfish farms and some other forms of aquaculture is a clear vector in further spread of unwanted marine species. NRC has thus far been slow to implement satisfactory controls on movement of used aquaculture equipment, or to bring in rules regarding decontamination before movement of equipment to other areas.

I would consider marine finfish farming only under a set of rules designed to completely isolate the farming activity from any chance of contamination of natural seawater or natural marine life stocks.

Such rules might look like this:

1. The facility must have no connection to the sea, and must be completely land-based.

2. Seawater could be transported to the facility, but no seawater can be released back to the sea. All seawater used in the facility must be treated to kill any disease organisms, to remove pollutants and any medical drugs, hormones and antibiotics, and disposed of in such a way that there is no chance of release to natural waterways or the sea.

3. There must be no release, deliberate or otherwise, of any live or dead fish stock or offal or uneaten food or faeces from the facility to the sea.

4. Food for the fish must be produced from sustainable land-based sources, supplemented in part where possible from genuine by-products of other sustainable marine fishing or aquaculture ventures. Fully integrated systems should be encouraged where possible.

5. There must be regular checks for compliance with all the above criteria by relevantly qualified personnel from an appropriate Government agency.